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1. Space Environment
Lecture 31 – Space Debris (Vol. 2)
CubeSats and Starlink
Professor Hugh Lewis
SESA3038 Space Environment

2. Overview of lecture 31
• In this lecture we look again at the impacts of CubeSats on the
environment, but this time with recent data from SOCRATES
– We compare to the results from the 2014 study from the previous lecture
• We also look at the impacts made by the deployment of the Starlink
constellation into the low LEO region (again using SOCRATES data). We
see:
– The number of conjunction events predicted involving Starlink
– The proportion of all conjunction events predicted involving Starlink
• I present results for conjunctions < 5 km and < 1 km
– Those less than 1 km are proxies for the number of collision data
messages that might be received from the 18th Space Control Squadron
– Note that predictions made by SOCRATES are subject to large amounts
of uncertainty
Space Environment – Space Debris (Vol. 2)

3. SOCRATES Space Environment – Space Debris (Vol. 2)
Celestrak: Satellite Orbital Conjunction Reports Assessing Threatening Encounters in Space
http://celestrak.com/SOCRATES/

4. CubeSats Space Environment – Space Debris (Vol. 2)
Data from SOCRATES January-February 2021 (note that these are predictions for a 7-day period)
• 174 unique CubeSats
identified in space object
catalogue (beginning
March 2021)
• Average of ~1.5
conjunctions < 5 km
predicted per CubeSat per
year
• ~2000 conjunctions < 5
km predicted per week
• ~80 conjunctions < 1 km
predicted per week
• Broadly in line with
2014 data & stable?

5. CubeSats Space Environment – Space Debris (Vol. 2)
Data from SOCRATES January-February 2021 (note that these are predictions for a 7-day period)
• About 1-in-25 of all
conjunctions < 5 km
reported
• Recall: in 2014 this
value was 1-in-20 (note
that different CubeSats
will now be
contributing)
• ~1-in-33 of all
conjunctions < 1 km
reported

6. Starlink Space Environment – Space Debris (Vol. 2)
Data from SOCRATES (note that these are predictions for a 7-day period)
• More than 5000
conjunctions < 5 km
predicted for the week
beginning 1 March 2021
(~720 events per day)
• These are conjunctions
predicted with other
space objects (payloads
and debris)
• The rate is increasing
non-linearly
• ~13,000 conjunctions < 5
km per week, including
Starlink-on-Starlink

7. Starlink Space Environment – Space Debris (Vol. 2)
Data from SOCRATES (note that these are predictions for a 7-day period)
• More than 200
conjunctions < 1 km
predicted for the week
beginning 1 March 2021
(~30 events per day)
• These are conjunctions
predicted with other
space objects (payloads
and debris)
• This rate is also
increasing non-linearly
• ~900 conjunctions < 1
km per week, including
Starlink-on-Starlink

8. Starlink Space Environment – Space Debris (Vol. 2)
Data from SOCRATES (note that these are predictions for a 7-day period)
• Proportion of all
conjunctions in the
SOCRATES report
(including Starlink-on-
Starlink):
• ~27% of all
conjunctions < 5 km
(1-in-3.7) and ~40%
of all conjunctions <
1 km (1-in-2.5)
• ~50% increase in the
number of
conjunctions reported
by SOCRATES

9. Starlink Space Environment – Space Debris (Vol. 2)
Data from SOCRATES (note that these are predictions for a 7-day period)
• Proportion of all
conjunctions in the
SOCRATES report
(excluding Starlink-on-
Starlink):
• ~11% of all
conjunctions < 5 km
(1-in-9) and ~9% of all
conjunctions < 1 km
(1-in-11)
• Also ~ 11% of
conjunctions< 1 km
affecting ACTIVE
spacecraft

10. Starlink Space Environment – Space Debris (Vol. 2)
Data from SOCRATES (note that these are predictions for a 7-day period)
• Number of unique
space objects involved
in conjunctions < 5 km
with Starlink
• ~1200 different
objects by March
2021

11. NASA data for the ISS: 1999-2020 Space Environment – Space Debris (Vol. 2)
• The number of ISS-
crossing objects
increases during solar
maxima
• Greater effects of
atmospheric drag
(debris “rain”)
• Solar cycle 25 is
starting
• What about Starlink?

12. Recap of lecture 31
• In this lecture we looked again at recent SOCRATES data for CubeSats and
Starlink
– CubeSat results have remained largely in-line with the results from 2014
(shown in the previous lecture)
– Approximately 1-in-20 to 1-in-25 of all conjunctions now involve
CubeSats
– Starlink is now dominating the conjunctions predicted by SOCRATES:
– Approximately 1-in-4 of all conjunctions < 5 km
– Approximately 1-in-2 to 1-in-3 of all conjunctions < 1 km
– The deployment of Starlink has led to a 50% increase in the number of
conjunctions in each SOCRATES report
– Collision avoidance should remove any threatening events, but the
burden could be high  autonomous systems needed
Space Environment – Space Debris (Vol. 2)